This invention relates generally to surveying equipment and more particularly to surveying equipment having lightweight and yet robust, precision construction.
Surveying equipment and particularly the support structure therefore must be able to withstand all kinds of environmental conditions while retaining its integrity and dimensional accuracy. In many instances, the dimensional accuracy is imperative in order to obtain the correct measurements in a geographic survey. For instance, prism poles and global positioning satellite (GPS) poles must be able to retain a substantially fixed position of extension as they are moved from place to place over uneven terrain and in all kinds of weather. Prism poles include two or more interfitting pole sections, and support a prism or other measurement device at the top used to sight or determine positions with laser, modulated infrared, angular and/or GPS position locators or like surveying systems. The prism reflects light back to the position locator for determining the location of the prism at different locations in a survey. The prism pole may be constructed with telescoping sections so that it may be collapsed to a reduced height (e.g., about four feet) for storage and transport, and then extended to its operating height which may be, typically, eight feet or more. In topological surveys, it is important that the pole be able to maintain its extended height as it is moved from place to place. It is therefore, critical to be able to lock the pole sections in a fixed position of extension in such a way as to have them stay. Moreover, the pole must maintain its longitudinal axis as it is extended so that its extended height is accurate every time. Similarly, the pole must be able to withstand numerous cycles of extension and retraction, and frequent rough handling while maintaining this accuracy. Still further, it is frequently desirable to completely detach the telescoping sections without substantial disassembly of the surveying pole or loss of accuracy upon reassembly.
The need for durability and accuracy has traditionally led to making surveying poles out of metal. However, metal poles can expand and contract significantly with changes in the temperature of the surrounding environment which is detrimental to accuracy of the survey. Metal poles are also capable of plastic deformation which can lead to inaccurate measurements. Carrying a heavy metal pole over uneven or broken terrain, as will be frequently necessary in surveying, can be very difficult and physically taxing. Using metal poles in the outdoors also presents a risk of lightening strike. It is possible to make poles out of lighter weight, non-conducting material, such as fiberglass, which are sturdy and weather-resistant. However, these poles will typically not withstand the clamping forces conventionally applied to metal poles to hold them in a fixed extension. Lower clamping forces may not adequately hold the pole sections in position. A similar problem is present when attaching something which must maintain a precise orientation, such as a level, to the pole. Non-metal materials may also be less likely to withstand impact forces associated with forcefully retracting the pole sections.
The surveying poles or other surveying equipment support structure may have telescoping sections, screw-together sections or a combination of the two. It is important to be able to rapidly collapse the poles for storage and transport. Also for cleaning in the field, the pole sections need to be able to be quickly and accurately disassembled and reassembled. Regardless of the material of the pole, it is often difficult to economically manufacture the pole sections so that they will maintain the same linear axis every time they are screwed together. One problem is the initial installation of screw fittings in ends of the pole sections. Care must be taken to achieve axial alignment upon installation. Another problem is the accumulation of debris on the fittings so that when screwed together, the fittings do not achieve face-to-face engagement which results in axial misalignment of the pole sections. For telescopingly interfitted pole sections, it is important to be able to easily disassociate the sections for cleaning or repair, and reassemble them while maintaining accuracy.
It is also not uncommon for these poles to have some accessory equipment. For instance, the bottom of a prism pole is conventionally equipped with a steel point to locate the pole on the ground. However in circumstances where the ground is soft, it is undesirable to have the point engaging the ground because the point tends to penetrate the surface of the ground. As a result, the location of the top of the pole above the ground can be inconsistent. Conventionally, the steel point has been removed and replaced with a blunt or greatly enlarged blunt end under these circumstances. The replacement involves several steps and it is necessary to carry the blunt end (or the steel point) around separately from the pole until used. The steel point can be difficult to safely carry because its point can be rather sharp.
Among the several objects and features of the present invention may be noted the provision of a lightweight surveying pole which is sturdy and weather-resistant; the provision of such a surveying pole which accurately maintains an extended height; the provision of such a surveying pole which maintains sections in a coaxial relation; the provision of such a surveying pole which can be disassembled and accurately reassembled for cleaning and repair; the provision of such a surveying pole which can be reconfigured with minimal steps; and the provision of such a surveying pole which can be efficiently manufactured with high accuracy.
Further among the several objects and features of the present invention may be noted the provision of a pole section for surveying equipment and a method of making such a pole section which is lightweight; the provision of such a pole section and method for making a pole section which can be repeatedly disassembled and accurately reassembled; and the provision of such a method which can be efficiently carried out with high accuracy.
Generally, a pole section constructed according to the principles of the present invention for use in surveying equipment is elongate and has opposite ends at least one of which is open. The pole section has an interior surface in the open end and a fitting received in the open end of the pole section. The fitting includes first and second spaced circumferential engagement surfaces in contact with the interior of the pole section for precisely locating the fitting relative to the pole section and a circumferential channel located between the engagement surfaces. The channel is spaced from the pole section, and an adhesive located in the channel and bonding the fitting to the pole section.
In another aspect of the present invention, a pole section for use in surveying equipment is elongate and having opposite ends at least one of which is open. The pole section has an interior surface in the open end and a fitting received and held in the open end of the pole section. The fitting is formed with a connector element adapted for connection with a corresponding connector element of another component of the surveying equipment. The fitting includes an axially facing end surface having a surface area and facing axially outward from the pole section. The axially facing surface including a peripheral engagement portion constitutes a first smaller portion of the axially facing surface area, and an axially recessed portion constitutes a second larger portion of the surface area recessed axially from the peripheral engagement portion thereby to facilitate full face-to-face engagement of the engagement portion with said other component of the surveying equipment.
In a still further aspect of the invention, a method of making a pole section for surveying equipment generally comprises the steps of providing an elongate member having opposite ends at least one of which is open and an interior surface inside the open end, and a fitting having an end surface, first and second spaced circumferential engagement surfaces, a circumferential channel located between the engagement surfaces and an adhesive passage opening at one end at the end surface of the fitting and at another end in the channel. The fitting is inserted into the open end of the elongate member such that the end surface faces axially outwardly of the open end of the elongate member and the circumferential engagement surfaces engage the interior surface and align the fitting with respect to the elongate member. Adhesive is injected through the adhesive passage from the end surface of the fitting as inserted into the elongate member into the channel for bonding the fitting to the elongate member.
Other objects and features of the present invention will be in part apparent and in part pointed out hereinafter.